Composite items are typically constructed from layers of material that are laminated together. The categories of materials utilized to fabricate or “layup” composite items include, for example: fiber, fabric, tape, film, and foil. Within each of these categories, a multitude of diverse materials are utilized. For example, fibers utilized include: glass, carbon, aramid, quartz, and the like. When arranged as woven sheets and unidirectional ribbons, the fibers are referred to as fabric and tape, respectively.
Fiber placement is a process used to construct or fabricate composite items. These composite items include relatively simple planar sheets or panels to relatively large complex structures. The composite items are generally built up from multiple layers or plies of composite materials that are pre-impregnated with uncured resin (“prepreg”). These plies are placed on a form by a head that is positioned by a positioning device such as a robotic arm or gantry.
Composite material are typically supplied in rolls or spools in a variety of widths. Generally, more highly contoured composite items are fabricated from relatively narrower composite materials. Composite materials having a width of about ⅛ inch to about 1 inch are typically referred to as “tow,” and often several strands of tow are placed at one time in order to lay down a wider strip. A head on a tow placement device arrays a group of prepreg tows into a continuous band and compacts them against the surface of the form or layup tool.
A disadvantage of conventional tow placement devices is that resin from the prepreg tows may foul components along the path from the spool to the compaction roller. Another disadvantage of conventional tow placement devices is that the head only dispenses one width of tow. When composite items requiring other tow widths are fabricated, another head may be required. Changing the width of the tow is a time consuming and labor intensive task.
Accordingly, it is desirable to provide a method and apparatus capable of overcoming the disadvantages described herein at least to some extent.